Webster's Revised Unabridged Dictionary · 1913

A Turkish or Persian monk, especially one who professes extreme poverty and leads an austere life.

One of the fanatical followers of the Mahdi, in the Sudan, in the 1880's.

in modern times, a member of an ascetic Muslim sect notable for its devotional exercises, which include energetic chanting or shouting and rhythmic bodily movement, such as whirling, leading to a trance-like state or ecstasy. From these exercises the phrase whirling dervish is derived.

figuratively, a person who whirls or engages in frenzied activity reminiscent of the dervish{3} dancing.